Encapsulated nanocompositions for increasing hydrocarbon recovery

ABSTRACT

A method for increasing production in a liquid hydrocarbon reservoir formation comprising the steps of introducing a nanoencapsulated composition solution capable of reducing the surface tension of a liquid hydrocarbon fraction, where the nanoencapsulated composition solution comprises a nanocapsule and a carrier fluid, such that the nanocapsule is dispersed in the carrier fluid; allowing the nanoencapsulated composition solution to interact with the liquid hydrocarbon fraction such that the surface tension of the liquid hydrocarbon fraction is reduced such that at least a portion of the liquid hydrocarbon fraction is capable of being displaced; introducing a water fraction into the wellbore under conditions such that at least a portion of the liquid hydrocarbon fraction is displaced from the liquid hydrocarbon reservoir formation; and recovering the at least a portion of the liquid hydrocarbon fraction and at least a portion of the nanoencapsulated composition solution using the wellbore.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Non-Provisional applicationSer. No. 15/093,923 filed on Apr. 8, 2016, which claims priority fromU.S. Provisional Application No. 62/145,219 filed on Apr. 9, 2015. Forpurposes of United States patent practice, this application incorporatesthe contents of both the Provisional Application and Non-ProvisionalApplication by reference in their entirety.

TECHNICAL FIELD

Compositions and methods are provided that relate to enhancing theproduction of subterranean hydrocarbon formations such as crude oilbearing formations. In some embodiments, compositions that relate tonanocompositions comprising surfactant compounds as well as methodsrelated thereto for increasing permeability, mobility and sweepefficiency within a reservoir for enhancing oil recovery are provided.

BACKGROUND

The oil and gas industry has greatly benefited from the use of enhancedoil recovery (EOR) processes, which increase the production ofunderperforming or problematic wells and fields. Many EOR processes arebased on chemical induced well stimulation and may include one or moreof (1) chemicals capable of inducing reservoir fractures and creatingnew or additional hydrocarbon flow channels for moving oil from aformation into a wellbore; (2) chemicals capable of dissolving portionsof the reservoir formation and creating alternative flow paths forhydrocarbons; and (3) chemicals capable of enhancing the flow of liquidhydrocarbons such as oil from a reservoir formation into the wellbore.

Surfactants are a commercially important class of compounds capable ofreducing the surface tension at liquid-liquid or liquid-solidinterfaces. The amphiphillic composition of surfactants allows for theirutilization as detergents, emulsifiers, dispersants, foaming agent,wetting agents and anti-coalescents. In the oil and gas industry,surfactants have been used in attempts to increase the conductivity orflow of liquid hydrocarbons in subterranean reservoirs for enhancing oilrecovery, e.g. following water flooding and/or steam flooding of asubterranean hydrocarbon bearing reservoir.

However, the use of techniques such as steam flooding can induce gravityoverride in the subterranean hydrocarbon bearing reservoir. Thereservoir heterogeneity generated by primary recovery techniques such assteam flooding is a well-established challenge in the oil and gasindustry, particularly for commercial entities involved in crude oilproduction and related downstream applications. In addition, thepresence of thief zones, formational fractures, high permeabilitystreaks and related geological formations within subterraneanhydrocarbon bearing reservoirs are continuing challenges in primary oilrecovery and EOR operations.

SUMMARY

The need therefore exists for methods and compositions capable ofincreasing EOR efforts for liquid hydrocarbon recovery. Compositions andmethods are provided that relate to enhancing the production ofsubterranean hydrocarbon formations such as crude oil bearingformations. In some embodiments, compositions that relate tonanocompositions comprising surfactant compounds as well as methodsrelated thereto for increasing permeability, mobility and sweepefficiency within a reservoir for enhancing oil recovery are provided.Described are nanoencapsulated compositions and related methods forincreasing production hydrocarbon bearing reservoirs.

In a first aspect, a method for increasing production in a liquidhydrocarbon reservoir formation is provided. The method includes thesteps of (a) introducing a nanoencapsulated composition solution capableof reducing the surface tension of a liquid hydrocarbon fraction into awellbore operably engaged with the liquid hydrocarbon reservoirformation. The nanoencapsulated composition solution includes ananocapsule and a carrier fluid, such that the nanocapsule is dispersedin the carrier fluid. The method further includes the steps of (b)allowing the nanoencapsulated composition solution to sufficientlyinteract with the liquid hydrocarbon fraction such that the surfacetension of the liquid hydrocarbon fraction is sufficiently reduced suchthat at least a portion of the liquid hydrocarbon fraction is capable ofbeing displaced from the liquid hydrocarbon reservoir formation; (c)introducing a water fraction into the wellbore under conditions suchthat at least a portion of the liquid hydrocarbon fraction is displacedfrom the liquid hydrocarbon reservoir formation; and (d) recovering theat least a portion of the liquid hydrocarbon fraction displaced from theliquid hydrocarbon reservoir formation and at least a portion of thenanoencapsulated composition solution using the wellbore.

In certain aspects, the nanocapsule includes two or more surfactantsselected from the group consisting of a sulfonate based surfactant, asulfate based surfactant and a phosphate based surfactant. In certainaspects, the nanocapsule includes petroleum sulfonate. In certainaspects, the nanocapsules are characterized by individual diameters ofbetween about 200 nanometers and about 1000 nanometers. In certainaspects, the nanoencapsulated composition solution is introduced intothe wellbore at a nanocapsule concentration in the range of about 0.01%by weight to about 10% by weight. In certain aspects, steps (a) through(d) above are repeated one or more times for enhancing the recovery of aresidual liquid hydrocarbon fraction from the liquid hydrocarbonreservoir formation. In certain aspects, the liquid hydrocarbon fractionincludes crude oil. In certain aspects, the method further includesintroducing a primary oil recovery composition for recovering a primaryliquid hydrocarbon fraction from the liquid hydrocarbon reservoirformation prior to step (a) above. In certain aspects, the primary oilrecovery composition is selected from water, natural gas, air, carbondioxide, nitrogen and combinations thereof. In certain aspects, themethod further includes introducing a deflocculant into the wellboreoperably engaged with the liquid hydrocarbon reservoir formation priorto step (c) above. In certain aspects, the deflocculant is selected fromthe group consisting of lignite, tannin, polycarbonate, polycarboxylate,polyacrylamide, sodium carboxymethyl cellulose, sodium citrate, sodiumsilicate, ammonium oxalate, sodium oxalate, gum arabic, humic acidresin, bentonite, and combinations thereof. In certain aspects, themethod further includes introducing a proppant into the wellboreoperably engaged with the liquid hydrocarbon reservoir formation priorto step (a). In certain aspects, the proppant is selected from the groupconsisting of sand, clay, bauxite, alumina and aluminosilicates andcombinations thereof. In certain aspects, the method further includesintroducing a dispersant into the wellbore operably engaged with theliquid hydrocarbon reservoir formation prior to step (a). In certainembodiments, the dispersant is selected from the group consisting oflignosulfate, polymethacrylate, hydroxypropyl methacrylatepolyacrylamide, sodium vinyl sulfonate, sodium acrylamidomethylpropanesulfonate, phosphonobutane tricarboxylic acid, amino trimethylenephosphonic acid, hydroxyethylidene diphosphonic acid, sodiumhydroxyethylidene diphosphonate, diethylenetriamine pentamethylenephosphonic acid and combinations thereof. In certain aspects, the methodfurther includes introducing a dispersant into the wellbore operablyengaged with the liquid hydrocarbon reservoir formation prior to step(c). In certain aspects, liquid hydrocarbon recovery is increased by atleast 10%.

In a second aspect, a method of forming a nanocapsule for use in ananoencapsulated composition solution is provided. The method includesthe steps of (a) mixing an aqueous-phase chemical with water to form anaqueous phase, (b) mixing a solvent-phase monomer with a solvent and oneor more surfactants to form a solvent phase, (c) dispersing the solventphase in the aqueous phase, such that the solvent phase forms dropletsin the aqueous phase and a surface of the droplets forms an interfacebetween the aqueous phase and the solvent phase, and (d) allowing theaqueous-phase chemical and the solvent-phase monomer to polymerize atthe interface to form a polymer shell, wherein the polymer shellencapsulates the one or more surfactants and the solvent.

In a third aspect, a coacervation method of forming a nanocapsule foruse in a nanocapsulated composition solution is provided. Thecoacervation method includes the steps of (a) mixing an aqueous-phasechemical with water to form an aqueous phase, where the aqueous-phasechemical includes gelatin, (b) mixing a solvent-phase monomer with asolvent and one or more surfactants to form a solvent phase, (c) mixingthe solvent phase in the aqueous phase, such that the solvent phaseforms droplets dispersed in the aqueous phase to form a mixture, wherethe droplets have a surface, (d) adding a precipitating agent to themixture, the precipitating agent operable to reduce a solubility of theaqueous-phase chemical in the mixture such that the aqueous-phasechemical is capable of precipitating from the mixture, (e) allowing theaqueous-phase chemical to precipitate from the mixture to form aprecipitating aqueous-phase chemical, where the precipitatingaqueous-phase chemical deposits on the surface of the droplets to form adeposited aqueous-phase chemical, and (f) allowing the depositedaqueous-phase chemical to form a polymer shell around the droplets,wherein the polymer shell is formed by the crosslinking of the depositedaqueous-phase chemical.

BRIEF DESCRIPTION OF THE DRAWING

So that the manner in which the features, advantages and objects of theembodiments as well as others which will become apparent, are attained,and can be understood in more detail, more particular descriptionbriefly summarized above may be had by reference to the embodimentsthereof which are illustrated in the appended drawing that forms a partof this specification. It is to be noted, however, that the drawingillustrates only a preferred embodiment and is therefore not to beconsidered limiting of its scope as there may admit to other equallyeffective embodiments. The preferred embodiment will be betterunderstood on reading the following detailed description of non-limitingembodiments thereof, and on examining the accompanying drawing, inwhich:

FIG. 1 is a scanning electron micrograph of sulfonate comprisingnanocapsules in accordance with some embodiments described.

DETAILED DESCRIPTION

Although the following detailed description contains specific detailsfor illustrative purposes, the skilled artisan will appreciate that manyexamples, variations and alterations to the following details are withinthe inventive scope and spirit. Accordingly, the exemplary embodimentsdescribed here are set forth without any loss of generality, and withoutundue limitations.

Compositions and methods for enhancing the production of subterraneanhydrocarbon formations such as crude oil bearing formations areprovided. A nanoencapsulated composition solution is introduced into awellbore, where the nanoencapsulated composition solution includes ananocapsule and a carrier fluid, such that the nanocapsule is dispersedin the carrier fluid. The nanocapsule includes one or more surfactantscapable of reducing the surface tension of a liquid hydrocarbon fractionin a liquid hydrocarbon reservoir formation. The methods can forincreasing permeability, mobility and sweep efficiency within areservoir for enhancing oil recovery. In preferred embodiments, thepresent invention relates to nanoencapsulated surfactant compositionsthat exhibit advantageous size and temporal controllability. Thecompositions, in some embodiments, demonstrate enhanced targeting ofsubterranean oil reservoirs via reduced adsorption in non-hydrocarbonbearing areas associated with or peripheral to a wellbore.

As used here, the term “surfactant” refers to a compound capable ofreducing the interfacial tension between two media, such as two liquidsor a liquid and a solid. A surfactant may refer to a cationic, anionic,zwitterionic or nonionic compound capable of behaving as a surfactant.In preferred embodiments, a surfactant is an anionic compound such as asulfonate.

As used here, the terms “sweep efficiency” and “volumetric sweepefficiency” refer to the efficacy of a process for increasinghydrocarbon recovery, including enhanced oil recovery (EOR) processes.

As used here, a “crosslinking agent” refers to a compound capable ofchemically bonding to and thereby connecting (“crosslinking”) two ormore individual polymers. In certain embodiments, the crosslinking agentmay form one or more covalent bonds with the polymers. A crosslinkingagent may bond to a polymer via a carbonyl, sulfhydryl, amine or iminechemical group on the crosslinking agent. A crosslinking agent is notlimited to any particular spacial arrangement and may, in certainembodiments, assume one or more of a linear, branched, blocked ordendrimeric structure prior to or following bonding to two or moreindividual polymers.

As used herein, “liquid hydrocarbon reservoir formation” refers to asubterranean reservoir formation that contains crude oil. Liquidhydrocarbon reservoir formation includes a hydrocarbon bearing formationand a liquid hydrocarbon bearing formation.

The term “solvent-phase monomer” refers to a monomer that is soluble inthe solvent phase and insoluble in the aqueous phase and is reactivewith the aqueous-phase chemical. For example, isocyanate is a monomerthat is soluble in dibutyl sebacate, but not in water.

The term “aqueous-phase chemical” refers to a monomer, gelling agent, ora chemical that is soluble in the aqueous phase and insoluble in thesolvent phase and is reactive with the solvent-phase monomer. An exampleof a chemical that can be used as the aqueous-phase chemical is gelatin.

The compositions and methods advantageously encapsulate surfactants. Itis understood by one of skill in the art that surfactants can beslightly water soluble so they bridge between the aqueous andnon-aqueous interface. In conventional surfactant operations,significant surfactant is lost due to adsorption by the rock near thewellbore area where there is a large amount of bare rock, but a smallamount of oil. Water soluble surfactants need to be encapsulated tomitigate the adsorption loss and the capsule must be small enough totraverse the oil reservoir. The methods and compositions provide for anano-sized encapsulated surfactant, where the encapsulated surfactantcan break out of the capsule, after certain periods of time, tosolubilize oil. The methods and compositions provide for the break outtime to be controlled by the toughness and the thickness of theencapsulation shell. The methods and compositions provide for a way tocontrol the release rate of surfactants.

The compositions and methods described address problems associated withthe recovery of liquid hydrocarbons from liquid hydrocarbon reservoirformations by injecting nanoencapsulated compositions capable ofreducing the surface tension of a liquid hydrocarbon fraction in theliquid hydrocarbon reservoir formation. The methods and compositionsdisclosed here advantageously increase primary liquid hydrocarbonrecovery efforts as well as enhanced oil recovery (EOR) processes forliquid hydrocarbons, particularly crude oil, following theirintroduction into a liquid hydrocarbon reservoir formation. In addition,primary recovery techniques such as water flooding may precede and/orfollow the introduction of the nanoencapsulated compositions such thatoverall liquid hydrocarbon recovery is increased.

While not limiting the embodiments to any particular physiochemicalproperties or characteristics, the methodologies and relatedcompositions described here may advantageously reduce the volume of thecompositions used to increase primary and/or EOR liquid hydrocarbonrecovery efforts as well as enhanced oil recovery (EOR) processes forliquid hydrocarbons as compared to previously disclosed or commerciallyavailable compositions for use in liquid hydrocarbon recovery.Advantageously and unexpectedly, the methodologies and relatedcompositions described here can be used to make sub-micron particles,that is particles with a diameter less than 200 nm. For instance, thenanocapsules can be synthesized with diameters as small as approximately20 nanometers (nm), which can reduce the treatment volume and associatedcosts and efforts for treating a subterranean reservoir formationbearing crude oil. One of skill in the art would understand that to beuseful in oil recovery, particles must be submicron sized.

In certain embodiments, the methods and compositions described hereadvantageously and unexpectedly enhance liquid hydrocarbon recovery byincreasing liquid hydrocarbon flow and conductivity for a liquidhydrocarbon fraction in a subterranean reservoir formation. Theformation may comprise complex geological formations such asheterogeneous reservoir formations which may prevent traditional primaryoil recovery and/or EOR techniques from effectively and economicallyinducing liquid hydrocarbon flow, e.g. via reduced (volumetric) sweepefficiency. The methods and nanoencapsulated compositions increaseliquid hydrocarbon flow, sweep efficiency and therefore liquidhydrocarbon recovery.

The nanoencapsulated composition solution is formed by mixingnanocapsules in a carrier fluid. An form of mixing can be used thatresults in the nanocapsules being dispersed in the carrier fluid. Thenanocapsule concentration is the amount of nanocapsules in the carrierfluid. The nanocapsule concentration can be in the range from about 0.01percent (%) by weight to about 10% by weight. In certain embodiments,the nanocapsule concentration can be about 1% by weight, alternately 2%by weight, alternately 3% by weight, alternately 4% by weight, andalternately 5% by weight.

A nanocapsule is a spherically shaped capsule that contains a polymershell surrounding two or more surfactants together with a solvent.

In a first method of making a nanocapsule, an interfacial polymerizationmethod is utilized. At least one surfactant and a solvent-phase monomerare added to a solvent to form a solvent phase. The amount of surfactantin the solvent phase can range from between about 1 wt % to about 50 wt%. The amount of solvent-phase monomer in the solvent phase can rangefrom between about 1 wt % to about 30 wt %. The solvents suitable foruse include iso-octane, acetone, dibutyl sebacate, and mixtures thereof.

Surfactants suitable for use include sulfonate based surfactants,sulfate based surfactants and phosphate based surfactants. Examples ofsulfonate based surfactants include petroleum sulfonate, dodecylbenzenesulfonate, and other alkyl sulfonates. Examples of sulfate basedsurfactants include sodium dodecyl sulfate and other alkyl sulfates.Examples of phosphate based surfactants include alkyl phosphates. Inembodiments where two or more surfactants are used, the two surfactantsare different from each other. In at least one embodiment, thesurfactant is petroleum sulfonate.

An aqueous-phase chemical is added to water to form an aqueous phase.The amount of aqueous-phase chemical in the aqueous phase can be in therange from 1 wt % to about 30 wt %.

The solvent phase is then dispersed in the aqueous phase. Any method ofdispersing the solvent phase in the aqueous phase that results informing droplets of the solvent phase in the aqueous phase can be used.Examples of methods to disperse the solvent phase include mixing,blending, and shaking. After adding the solvent phase to the aqueousphase, the aqueous phase contains droplets of solvent phase throughout.The solvent phase and aqueous phase can be immiscible to each other. Thesurface of the droplets forms the interface between the solvent phaseand the aqueous phase.

The polymer shell forms from the reaction of the solvent-phase monomerand the aqueous-phase chemical due to interfacial polymerization. Ininterfacial polymerization, the solvent-phase monomer and theaqueous-phase chemical “see” each other at the interface and polymerizeat the interface to form the polymer shell. Because the polymer shellforms at the interface of the solvent phase droplet, the polymer shellencapsulates the droplet and in doing so encapsulates the solvent andsurfactant in the solvent-phase droplet. The use of a solvent-phasemonomer and an aqueous-phase chemical unexpectedly generated nanosizedcapsules.

The use of a solvent-phase monomer and an aqueous-phase chemicaladvantageously formed nanocapsules that are nano-sized particles. Thenanocapsules can be characterized by individual diameters of betweenabout 200 nanometers and about 1000 nanometers.

In at least one embodiment, the aqueous phase is the continuous phaseand after reaction the resultant nanocapsules can be dispersed in theaqueous phase forming a nanocapsule dispersion. The nanocapsuledispersion can be mixed into the carrier fluid to form thenanoencapsulated composition solution that can be used for oil recovery.

In embodiments employing the interfacial polymerization method, theshell thickness of the polymer shell can be controlled. The shellthickness can be controlled by the amount of aqueous-phase chemical andsolvent-phase monomer used. Shell thickness can be increased byincreasing the concentration of aqueous-phase chemical and solvent-phasemonomer.

In a second method of forming a nanocapsule, the polymer shell is formedby a coacervation method. In embodiments employing the coacervationmethod, the aqueous-phase chemical is gelatin, which is mixed with waterto form the aqueous phase. At least one surfactant and a solvent-phasemonomer are mixed with the solvent to form the solvent phase. Thesolvent phase is dispersed in the aqueous phase in the form of droplets.After the solvent phase is dispersed in the aqueous phase in the form ofdroplets, a precipitating agent is added to the mixture. Theprecipitating agent changes the solubility of the gelatin in water,causing the gelatin to precipitate out as a precipitating aqueous-phasechemical. In at least one embodiment of the present invention, theprecipitating agent is a salt and this is known as a “salting out”phenomenon. The precipitating aqueous-phase chemical deposits onnon-aqueous surfaces, such as the surface of the droplets of the solventphase to form a deposited aqueous-phase chemical. The depositedaqueous-phase chemical then forms the polymer shell due to crosslinkingaround the droplets and encapsulates the droplets of the solvent phase.In at least one embodiment, the precipitating agent is ammonium sulfate.

In embodiments employing the coacervation method of formingnanocapsules, the degree of crosslinking of the polymer shell can becontrolled. The degree of crosslinking of the polymer shell can becontrolled by adding an amount of crosslinking agent. The crosslinkingagent can be glutaraldehyde. The degree of crosslinking can be measuredby the amount of swelling of the polymer or the rate of degradation. Thegreater the degree of crosslinking the less a polymer particle isexpected to swell. The greater the degree of crosslinking the slower therate of degradation or disintegration of the polymer particle in hotwater.

In the methods of forming nanocapsules, the solvent phase and theaqueous phase can be heated as needed to increase dispersion or initiateformation of the polymer shell. The methods and compositions describedhere are in the absence of the use of a fluidized bed to encapsulate theparticles. The methods and compositions described to form thenanocapsules are in the absence of the use of polymer as a raw material.

The nanoencapsulated composition solutions can be mixed with a carrierfluid used for increasing production in a liquid hydrocarbon reservoirformation. In at least one embodiment, the nanoencapsulated compositionsolution can include nanocapsules, water, and other productionchemicals. The nanoencapsulated composition solution is introduced intothe liquid hydrocarbon reservoir formation. The nanoencapsulatedcomposition solution is introduced into the wellbore at a concentrationof between about 0.01% by weight and about 10% by weight of thenanoencapsulated composition solution, alternately at a concentration ofabout 1% by weight of the nanoencapsulated composition solution,alternately at a concentration of about 2% by weight of thenanoencapsulated composition solution, alternately at a concentration ofabout 3% by weight of the nanoencapsulated composition solution,alternately at a concentration of about 4% by weight of thenanoencapsulated composition solution, and alternately at aconcentration of about 5% by weight of the nanoencapsulated compositionsolution. In at least one embodiment, the nanoencapsulated compositionsolution is introduced to a wellbore that is fluidly connected to aliquid hydrocarbon reservoir formation. In at least one embodiment, thewellbore is an injection well that is part of a pairing that includes aninjection well and a recovery well.

The nanoencapsulated composition solution is allowed to interact withthe liquid hydrocarbon fraction in the liquid hydrocarbon reservoirformation for a residual time period. In at least one embodiment, theliquid hydrocarbon fraction is crude oil. In at least one embodiment,the liquid hydrocarbon fraction is crude oil and the portion of liquidhydrocarbon fraction is an amount of crude oil. The polymer shell of thenanocapsule degrades over time with exposure to heat. As the polymershell degrades, the one or more surfactant is released from thenanocapsule, which depletes the nanocapsule. The one or more surfactantreduces the surface tension of the liquid hydrocarbon fraction. Byreducing the surface tension, the liquid hydrocarbon fraction can bedisplaced from the liquid hydrocarbon reservoir formation. The residualtime period can be between about 0.1 days (2.4 hours) and about 300days, alternately the residual time period can be about one (1) day,alternately between about one (1) day and about seven (7) days,alternately about seven (7) days, alternately between seven (7) days andabout thirty (30) days, alternately about (30) thirty days, andalternately about 180 days.

In a next step of the method for increasing production in a liquidhydrocarbon reservoir formation, a water fraction is introduced to thewellbore following the residual time period. The water fraction isintroduced at a pressure that causes a portion of the liquid hydrocarbonfraction to be displaced from the liquid hydrocarbon reservoirformation. In at least one embodiment, the water fraction floods thewellbore. In at least one embodiment, the water fraction is introducedto the injection well and pushes the liquid hydrocarbon fraction fromthe liquid hydrocarbon reservoir formation. In at least one embodiment,the water fraction floods the liquid hydrocarbon reservoir formation.

The portion of the liquid hydrocarbon fraction that is displaced fromthe liquid hydrocarbon reservoir is recovered as a recovered. In atleast one embodiment, the portion of the liquid hydrocarbon fractionthat is displaced from the liquid hydrocarbon reservoir is recoveredfrom the recovery well. In at least one embodiment, the recovered fluidcan include the portion of the liquid hydrocarbon fraction recovered andan amount of the nanoencapsulated composition solution.

The steps of the method can be repeated to enhance the recovery of aresidual liquid hydrocarbon fraction from the liquid hydrocarbonreservoir formation. The residual liquid hydrocarbon fraction refers tothe liquid hydrocarbon fraction remaining in the liquid hydrocarbonreservoir formation following a production method. In at least oneembodiment, the residual liquid hydrocarbon fraction equals thedifference between the liquid hydrocarbon fraction minus the at least aportion of the liquid hydrocarbon fraction that is recovered. The methodfor increasing production results in a liquid hydrocarbon recovery thatis increased by at least 10%, alternately by at least 20%, alternatelyby at least 50%, and alternately by at least 75%.

The method for increasing production can include additional steps. In atleast one embodiment, a primary oil recovery composition for recoveringa primary liquid hydrocarbon fraction from the liquid hydrocarbonreservoir formation can be introduced to the wellbore prior to the stepof introducing the nanoencapsulated composition solution. The primaryoil recovery composition can include water, natural gas, air, carbondioxide, nitrogen, and combinations thereof. In at least one embodiment,a proppant can be introduced prior to the step of introducing thenanoencapsulated composition solution. The proppant can include sand,clay, bauxite, alumina, aluminosilicates, and combinations thereof. Inat least one embodiment, a dispersant can be introduced to the wellboreprior to the step of introducing the nanoencapsulated compositionsolution. The dispersant can include lignosulfate, polymethacrylate,hydroxypropyl methacrylate polyacrylamide, sodium vinyl sulfonate,sodium acrylamidomethylpropane sulfonate, phosphonobutane tricarboxylicacid, amino trimethylene phosphonic acid, hydroxyethylidene diphosphonicacid, sodium hydroxyethylidene diphosphonate, diethylenetriaminepentamethylene phosphonic acid and combinations thereof.

In at least one embodiment, a deflocculant can be introduced to thewellbore prior to the step of introducing a water fraction into thewellbore. The deflocculant can include lignite, tannin, polycarbonate,polycarboxylate, polyacrylamide, sodium carboxymethyl cellulose, sodiumcitrate, sodium silicate, ammonium oxalate, sodium oxalate, gum arabic,humic acid resin, bentonite, and combinations thereof. In at least oneembodiment, a dispersant can be introduced to the wellbore prior to thestep of introducing a water fraction into the wellbore. The dispersantcan include lignosulfate, polymethacrylate, hydroxypropyl methacrylatepolyacrylamide, sodium vinyl sulfonate, sodium acrylamidomethylpropanesulfonate, phosphonobutane tricarboxylic acid, amino trimethylenephosphonic acid, hydroxyethylidene diphosphonic acid, sodiumhydroxyethylidene diphosphonate, diethylenetriamine pentamethylenephosphonic acid and combinations thereof.

The methods and nanoencapsulated compositions can beneficially besupplemented with one or more additional compositions capable ofincreasing liquid hydrocarbon recovery or targeting of the liquidhydrocarbon fraction of the subterranean reservoir formation by thenanoencapsulated compositions described. In non-limiting embodiments,these additional compositions include but are not limited to surfactantssuch as hydrocarbon based surfactants, sulfonate based surfactants,sulfate based surfactants and phosphate based surfactants.

EXAMPLES

The following examples are included to demonstrate preferredembodiments. It should be appreciated by those of skill in the art thatthe techniques and compositions disclosed in the examples which followrepresent techniques and compositions discovered by the inventors tofunction well, and thus can be considered to constitute preferred modesfor its practice. However, those of skill in the art should, in light ofthe present disclosure, appreciate that many changes can be made in thespecific embodiments which are disclosed and still obtain a like or asimilar result without departing from the inventive spirit and scope.

Example 1

Preparation of Nanocapsules I. In Example 1, petroleum sulfonatenanocapsules were prepared. The aqueous-based chemical was gelatin andwas mixed with water to produce a 5% aqueous gelatin solution as theaqueous phase. The solvent phase was produced by mixing 100 grams (g) ofiso-octane (as a solvent), 40 g of acetone (as a second solvent) and 5%Polartech® Fusion 460 (Afton Chemical, Richmond, Va.) as the source ofpetroleum sulfonate as the surfactant. One hundred (100) grams of theaqueous phase was heated to a temperature of 60° C. to help dissolve thegelatin, followed by the addition of 100 grams of the solvent phase and100 grams of 20% ammonium sulfate and vigorously stirred using amagnetic stirrer for two (2) hours at 60° C. The ammonium sulfate acteda precipitating agent to aid precipitation of the gelatin from theaqueous phase. Five (5) grams of 25% glutaraldehyde (as a crosslinkingagent) were then added to the mixture, and the resulting solution wasallowed to cool overnight to room temperature. The resultingnanocapsules that were collected exhibited diameters in a range of fromabout 200 nanometers (nm) to one (1) micrometer (μm) as determined usinga Quanta Model 250 FEG scanning electron microscopy (SEM) (FEI,Hillsboro, Oreg.).

Example 2

Preparation of Nanocapsules II. In an alternative methodology, petroleumsulfonate based nanocapsules were synthesized. The solvent phase wascreated by initially mixing 40 grams of dibutyl sebacate (Sigma Aldrich,St. Louis, Mo.) (as the solvent), 10 grams of toluene diisocyanate(Sigma Aldrich, St. Louis, Mo.) (as the solvent-phase monomer), 12 gramsof polyvinyl alcohol (Sigma Aldrich, St. Louis, Mo.) (as thesolvent-phase monomer) and 10 grams of EOR2095 (Chemtura Chemicals,Philadelphia, Pa.) as a source of petroleum sulfonate (as thesurfactant) in 250 ml deionized water under vigorous stirring for twenty(20) minutes at room temperature using a magnetic stirrer. 250 ml ofdeionized water and a 40 ml solution of 20% aqueous triethylenetetramine(TETA) (as the aqueous-phase chemical) were added to the solution. Thesolution temperature was then increased to 55° C. and vigorously stirredfor 3 hours, resulting in a colloidal dispersion. The resultingdispersion was diluted with approximately 450 ml of deionized water,resulting in a petroleum sulfate concentration of approximately 10,000ppm in the nanoencapsulated composition solution. As shown in FIG. 1,the dispersion comprised nanocapsules ranging in diameter from about 20nm to about 200 nm.

Example 3

Properties of Nanocapsules I. The nanocapsules of Example 1 were placedin a 90° C. oven, with the resulting petroleum sulfonate concentrationrecorded after 20, 48, 116, 140, 260, 468 and 596 hours (Table I) usinga Mitsubishi Model NSX-2100V sulfur analyzer (Mitsubishi Corporation,New York, N.Y.). While not limiting to any particular theory ortheories, it is believed that the observed increases in concentration ofpetroleum sulfonate over time are attributable to the increased presenceof petroleum sulfonate in a continuous (non-dispersed) phase that canadvantageously disperse following the injection of the nanocapsules intoa subterranean reservoir or related downhole formation.

TABLE I Time dependent measurement of petroleum sulfonate concentration(in ppm) in nanocapsules following heating at T = 90° C. Time elapsedPetroleum sulfonate (hours) concentration (ppm) 0 1007 20 2324 48 3560116 3560 140 3560 260 4165 428 5240 596 6181

Example 4

Properties of Nanocapsules II. The methods and compositions were furtherevaluated for some embodiments related to secondary and tertiaryenhanced oil recovery. A subterranean reservoir formation comprisingsedimentary rock core was subjected to a primary crude oil recoveryprocedure (water flooding) and exhibited a residual oil saturation levelof approximately 60% following water flooding. The sedimentary rock corewas subsequently injected with the nanoencapsulated composition solutionof Example 2 using fresh water under ambient conditions such that theresulting pore volume of the sedimentary rock core with the dispersednanocapsule composition was approximately 40%. The sedimentary rock corecomprising the nanoencapsulated composition solution was then heated to90° C. for approximately 168 hours (seven (7) days) such that rupturingof the nanocapsules was induced. The sedimentary rock core was thenflooded with approximately 100 ml of fresh water under ambientconditions, resulting in a crude oil recovery of approximately 3% withrespect to total estimated crude oil volume. The sedimentary rock corewas then flooded with one (1) equivalent pore volume of a 1% petroleumsulfonate solution at room temperature, which did not result in anyfurther, measurable crude oil recovery.

Although the embodiments have been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade hereupon without departing from the inventive principle and scope.Accordingly, the scope of the embodiments should be determined by thefollowing claims and their appropriate legal equivalents.

The singular forms “a”, “an” and “the” include plural references, unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently describedcomponent may or may not be present or the event or circumstances may ormay not occur. The description includes instances where the component ispresent and instances where it is not present, and instances where theevent or circumstance occurs and instances where it does not occur.

Ranges may be expressed here as from about one particular value, or toabout another particular value. When such a range is expressed, it is tobe understood that another embodiment is from the one particular valueand/or to the other particular value, along with all combinations withinsaid range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art, except when thesereferences contradict the statements made here.

What is claimed is:
 1. A coacervation method of forming a nanocapsulefor use in a nanocapsulated composition solution, the coacervationmethod comprising the steps of: (a) mixing an aqueous-phase chemicalwith water to form an aqueous phase, wherein the aqueous-phase chemicalcomprises gelatin; (b) mixing a solvent-phase monomer with a solvent andone or more surfactants to form a solvent phase; (c) mixing the solventphase in the aqueous phase, such that the solvent phase forms dropletsdispersed in the aqueous phase to form a mixture, wherein the dropletshave a surface; (d) adding a precipitating agent to the mixture, theprecipitating agent operable to reduce a solubility of the aqueous-phasechemical in the mixture such that the aqueous-phase chemical is capableof precipitating from the mixture; (e) allowing the aqueous-phasechemical to precipitate from the mixture to form a precipitatingaqueous-phase chemical, wherein the precipitating aqueous-phase chemicaldeposits on the surface of the droplets to form a depositedaqueous-phase chemical; and (f) allowing the deposited aqueous-phasechemical to form a polymer shell around the droplets, wherein thepolymer shell is formed by the crosslinking of the depositedaqueous-phase chemical.
 2. The method of claim 1, wherein an amount ofthe one or more surfactants in the solvent phase is in a range frombetween 1 wt % to 50 wt %.
 3. The method of claim 1, wherein the one ormore surfactants are selected from the group consisting of a sulfonatebased surfactant, a sulfate based surfactant and a phosphate basedsurfactant.
 4. The method of claim 1, wherein the one or moresurfactants comprises petroleum sulfonate.
 5. The method of claim 1,wherein an amount of the solvent-phase monomer in the solvent phase isin a range from between 1 wt % to 30 wt %.
 6. The method of claim 1,wherein the solvent is selected from the group consisting of iso-octane,acetone, dibutyl sebacate, and combinations thereof.
 7. The method ofclaim 1, wherein an amount of the aqueous-phase chemical in the aqueousphase is in a range from between 1 wt % to 30 wt %.
 8. The method ofclaim 1, wherein the aqueous-phase chemical is selected from the groupconsisting of monomer, gelling agent, chemical soluble in the aqueousphase and insoluble in the solvent phase, and combinations of the same.9. The method of claim 1, wherein the precipitating agent is selectedfrom the group consisting of salts, ammonium sulfate, and combinationsof the same.
 10. The method of claim 1, wherein the nanocapsules arecharacterized by individual diameters of between 200 nanometers and 1000nanometers.
 11. The method of claim 1, further comprising the step of:adding an amount of a crosslinking agent, wherein the crosslinking agentcan control a degree of the crosslinking of the polymer shell.
 12. Themethod of claim 10, where the crosslinking agent comprisesglutaraldehyde.